Luminous sign electrode



` Feb 3,'1942-- s. c, MILLER i LUMINoUs SIGN ELECTRODE Filed Feb. 12,1958 2 Sheets-Sheet 2 INVENTOR. SAMUU. C. MAL/ ER /A ATTORNEY Psa-'nadFeb, 3, `1942 UNITED STATE sf PATENT OFFICE 8 Claims.

This invention relates toelectrodes; more particularly to electrodesfor'luminous signs, such as neon sign construction, and to methods ofmaking the same; more particularly, to a metal-toglass sealed electrodeemployed in luminous tubes operating, with an ionizable inert gasfilling, to obtain a gaseous discharge producing a luminous effect underhigh potential electrical exciting force. f

Electrodes employed in electrical discharge devices of the charactermentioned, as known to me, have attendant problems in their manufactureand operation in addition to the cost of their production. Suchconstruction usually involves an electrode shell to which there areaffixed leads and sealed within a glass. envelope. Electrode devices ofthis character are more particularly illustrated inthe patent to LohmanNo. 1,739,513 and my Patent No. 2,'o64,485. The specic features of thesedescribed electrodes have been devised to cure problems in operatingconditions and in manufacturing operations particularly due to theexposure of the interior and exterior surfaces of the shell electrodewithin the zone of activity within the sealed glass envelope,

As desirable as these constructions may be, they offer additionalproblems in cost and construction in order to introduce these assembliesin the final sign in the electrical connections th'at may be required toconduct the electrical current to the electrodes.

I have discovered that the full benefits of a cup-shaped electrode,scalable directly to glass,

may be made available and provide an electrode from metaltoglass sealingcompetitively priced with sealed-in glass electrode shells by theemployment of h'eat resisting stainless steels which are characterzed'bytheir resistance to oxidation at elevated temperatures necessary forprocessing the luminous tube assembly and which metal is furthercharacterized by the formation of oxidized scale with great difficultyat high temperatures but which, nevertheless, provides scale of suchadherence as not to fiake off and interfere with a metal-to-glass sealjoint;

that sfurther characterized by a coefficient of expansion suitable forjoining to glass of thc character employed in neon discharge devices.

Such metal which' I have discovered is suiti able for the production ofcup-shaped metalto-glass scalable electrodes is exemplified in a h eat,resisting chromiumv steel, more particularly a chromium steel having thecharacteristics identified as Allegheny 55, the typical analysis forwhich'is more specifically described in Bulletin 55, Allegheny Steel Co.1934, and includes from 23 to 30% of chromium, with carbon .25%,manganese 1.00%; phosphorus .025%; .025%, silicon .50% and th'e balanceiron.

This metal, I have further discovered, is readily wetted by fused glassat temperatures necessary for working glass of the character employed inneon discharge tube signs and has sufficient resistance to deformationat temperat es necessary for processing by bombarding he completed andsealed discharge tube assembly.

Apart froml the discovery hereinabove mentioned, my invention resides inthe provision of a cup-shaped electrode of a `configuration amenable toeiecting a seal of glass-to-metal by commercial quantity productivemethods. to provide a competitive item with the sealed-in glass shellelectrodes. I

A still further object of my invention resides in the provision of aluminous or gaseous discharge tube electrode assembly comprising a deepdraw cup-shaped electrode of metal sealed to glass, which makes forcompactness and economy in construction, while not diminishing thesurface area of the electrode, thereby to give long life, as required inthe trade, and further to minimize sputtering, which interferes withrefinements in working conditions, particularly in connection withfluorescent tubes, where the sputtering effect would defeat and destroyor reduce the life of tubes of such character.

Other objects of my invention reside in the provision of an electrodeassembly and a method of assembly which eects material economies bysimplification of construction while achieving long life and 4extendedperformance in operpointed out, I make reference to the accompanyingdrawings, forming a part hereof, in which- Figure 1 is a fragmentary,longitudinal sectional view of the partsifor making the electrode, inaccordance with one embodiment of my invention;

Figure 2 is a fragmentary longitudinal sectional view, with th'e partsconnected and sealed together; v

Figure 3 is a section taken on the Figure 2;

Figure 4 is' a fragmentary longitudinal sectional view of anotherembodiment `of my inline 3-3 of sulphur vention, showing theparts'immediately before assembly;

Figure 5 is a fragmentary longitudinal sectional view of the partsillustrated in Figure 4,

brought together and assembled;

Figure 6 is a fragmentary longitudinal sectional view of the embodimentillustrated in Figures i, 2 and 3, assembled in position with anelectrode insulator housing;

Figure 7 is a fragmentary longitudinal -sectional view of .anotherembodiment of my invention;

Figures 8, 9 and 11 are fragmentary longitudinal sectional views ofthree additional embodiments of my invention;

- as illustrated in Figure 2 and the joining of the A section of theglass I0 at its open end'to a glass In this construction, theproportions of the s .parts are shown for Joining approximately a 15 mm.diameter glass tubing II). to a shell electrode II.' The shell electrodeis cup-shaped andhas cylindrical walls I2 and a bottom Il of integralconstruction, `joined to each other bythe rounded edge I4, during thedrawing operation, employing a metal more specically hereinafterdescribed.

Adjacent the mouth or opening I5, `the walls I2 are provided with afiare portion I6. The extensiveness of the flare is calculated to havethe smallest diameter adjacent the throat I1 slightly smaller than theouter diameter of the tubing III. 'I'he diameter of the mouth I5 isslightly larger than the outer diameter" of the tubing Il, with suchtolerance as to take care of the variation in size encountered inconnection with the tubing I0, and such variations in roundness as maybe encountered in the trade in connection with glass tubing used forluminous sign constructions. With these parts so provided, and the shellII mounted upon a. glass workers lathe, a section of tubing Iii may alsobe mounted upon a chuck of a glass worker's lathe equipped with blowingmeans, and while'the shell II and the tubing Il .are heated adjacent themouth I5 and the edge I8 by the glass workers flame, the parts arebrought together until the edge Il, nests within the flare I6. A JointI9, as illustrated in Figure 2, will thereby be obtained, of intimateand secure contact. 'Ihe flare ln relation to the edge I8 of the tubingprovides for a wiping action between the glass and the flared portion ofthe.

shell, to give the requisite wetting action of the glass upon the metal.The minimum` amount of attention isrequired by the glass blower or theminimum amount of accuracy is required in aligning the parts of theglass workers lathe where automatic machinery may be employed, as anyvariation in size of the glassin its diameter, as may be encountered inits production or by reason of its fusion during operation will beaccommodated by the flare I6 in bringing these parts together in theJoining of the twoat the fusion or melting temperature. An emcient andeffective seal is thereby provided, par- 75 is tubing sign assembly, thesign is processed by evacuating the air and heated to the point whereal1 the impurities are driven out of the inside of the tubing. Theelectrodes are connected to a high voltage transformer while drawing outthe air, until a discharge takes place between the electrodes. broughtto a bright red heat, approximately 900 C., and the juncture of theglass to metal must be sufficient to prevent collapsing of the glass aswell as the metal. The employment by me of the tapered or flared glassto metal juncture and the cup-shaped electrode of the metal hereinafterto be more specifically described, assures a maintenance of the sealduring this rigid processing operation. This I attribute not only to theformation of the seal `as already described, but also to thecharacteristics of the cup-shaped metal electrode which I have provided.

When so assembled as part of a sign and associated with the sign frame20, the electrode housing insulator 2I and pressed against the contactspring 22 of anassembly more specifically described and illustrated inmy Patent No. 2,046,960, July 7, 1936, an exceedingly compactarrangement is provided in that the shell I I may be brought intoimmediate contact with the contasting spring 22 without any furtherprovision iorbringlng these members into electrical conducting andcontacting connection.

The depth of the cup-shaped electrode provides all of the requisitesurface area on the interior surface of the assembly, to give the longlife and requisite discharge for maintaining operating conditions forluminosity. The. likelihood for sputtering is minimized and where thesign assembly is used in connection with fluorescent glass tubing orglass tubing coated with nuorescentvcompositlons, the elimination ofsputtering in conjunction with any mercury vapor yet further insureslong life of fluorescent signs.

While I have described and illustrated in Figures 1, 2 and 3, mypreferred construction which is most amenable for quantity productionmeth` ods in the` formation of the sea] joints of glass to metal and forother purposes hereinbefore described, an important contributing factorof my invention lies in the discovery of a commercially practical metalfrom which the cup-shaped electrodes may be formed. Accordingly, wherequantity production methods for forming the juncture or seal between theglass and metal are not of vital Vmoment and where it may be desired toobtain some of the features of my invention. a simple cylindrical shell23 may be provided. This shell diners from that heretofore described inthat no flare need be provided at the mouth or adjacent the edges 2l.The metal throughout may be of uniform thickness where I employ a shellmade from Allegheny-55 metal, hereinbefore described, and which, forpurposes of reference, I will designate as chromium steel.

The preferred alloy constitution of Alleghenyhas already been given andwhile this metal heat resisting, drawn.

During this operation, the metal is known to resist high heat. it hasnever been employed for the purposes discovered by me in that this metalhas-been regarded as not suited for deep drawing. Any contour whichinvolves difficult fabrication steps, such as deep drawing operations,has not been regarded as-the field for the employment of Allegheny-55 orsimilar heat resisting chromium steel. However, extended effortsinvolving more or less minute progressive changes in forming this metalhave led to the discovery of the successful adaptation of this metal fordeep draw, cup-shaped electrodes in which the full rigidity of the metalmay be emi ployed without resorting to the need for tapering the metalitself in order to provide what is generally referred to as aHousekeeper seal.

Thus in the embodiment illustrated in Figure '7, the walls of the shell23 may be maintained of uniform thickness to the edges 24 where heatresisting, drawn chromium steel of the character herein described isemployed. With such shell, the tubing Illa may be brought together withthe shell 23 to form the seal IBa, in which the glass is fused on theexterior and interior surfaces. The uniform depth D of the metalthroughout its length, to and including the edges 24, provides a rigidjoint of requisite strength which has heretofore rendered the taperedmetal employed-in Housekeeper seals impractical.

During the processing step or bombarding step in making the completesign wherein the metal is almost brought to a bright red temperature,the thickness D of the metal, at the point where it is embedded in theglass at the joint Isa, will prevent collapsing of the metal to glassjuncture.

Thus, where speeds of operation and production for making the seal ofglass to metal are not of vital moment, the employment of the heatresisting drawn chromium steel of the character herein described,especially using the uniform thickness of metal D to and including theedges 24, makes possible the employment of this metal for a metal toglass seal while utilizing the extended area as obtained by a deepdrawshell.

For other embodiments of my invention particularlyl conducive toquantity production methods, I have illustrated other forms of deep drawshell electrodes for the formation of metal to glass sea'iableelectrodes.

In Figures 4 and 5 there is described a shell electrode IIb, in which atapered section I6b is formed from the throat Hb.

In joining a tubing |013 with the cup-shaped electrode I Ib of thecharacter described, during.

the sealing operation involving the heating of the glass and metaladjacent the edge I8b and the mouth I5b, the shellelectrode is nested tocontact with the interior surface of the tube Ib to provide a joint I9b,more speciflcallyillustrated in Figure 5.

Here again, wide tolerance in sizes is permissible to make possiblespeeds of production practical for, economical operation, and a thoroughwetting of the glass to the metal, to give the desired weld due to thewiping action encountered in the tapered joint I 6b and the flare givento the glass in joining the glass tubing Ilib to the shell IIb.

Where employing tubing of about 15 mm. dil interior wall of the glasstubing Inc.

through the tubing, during the processing or bombarding operation, isaround 300 milliamperes, it may be desirable, especially where the jointis of the type Where the metal is on the interior of the glass, toprovide a surface configuration of the shell to minimize the attack ofthe discharge upon the glass at the point of contact of the metal.

For this purpose, reference is made to the embodiments illustrated inFigures 8 to 12, the constructions whereof have 'been devised to use thehigh currents specified, or longer durations ofY time of treatment, andto minimize anisr adverse effect upon the juncture of the metal toglass.

In the vembodiment illustrated in Figure 8, a shell electrode IIc isemployed, of the general character illustrated in Figures 4 and 5. Inthis construction, however, the tapered portion I6c is extended to leavea lip I5c, spaced from the This constricted mouth, spaced from thejuncture of the glass to metal Isc, allows the discharge during theprocessing or bombarding operation to go-inside the shell and minimizethe temperature at the juncture Isc.

Another form of construction to minimize the temperature at the glassjuncture is illustrated in Figure 9 wherein an electrode shelli Id isprovided at its mouth with a flange IBd,v substantially at right anglesto the wall of the shell I Id. Here the metal t0 glassjoint iSd may beformed by a pressing operation of the edge of the glass I8 to the flangeISd, to obtain a lap joint and a butt joint instead of the tapered lapjoint of the embodiments illustrated in Figures 1 to 5 and 8.

In Figures l1 and 12 I have illustrated a shell electrode of the samegeneral character as described in connection with Figures 1, 2 and 3.For purposes of minimizing the discharge and increase in temperatureadjacent the juncture I9, I provide a deilecting member 25, in the formof a rod, extending axially in the shell electrode I Ie so that its end26 is adjacent the mouth of the shell and its opposite end 21 contactsthe bottom I3e. I may aflix the rod 25 in any suitable manner,preferably by spot welding the end thereof 21 to the bottom I3e, asshown at the point 28.

In operation, during processing or bombarding, especially employing thecurrent through the tubing around or in excess of 300 milliamperes, theheat of the discharge will be absorbed first by the rod 25, to minimizethe high temperature adjacent the juncture I9, made by metal to glass bythe gradual conduction of the heat incident to the bombardment from therod and then through the shell.

It will thus be observed that I have provided a new and novel electrodeof simple and compact construction incident to the discovery of theemployment of the cup-shaped heat resisting drawn chromium steelelectrode, and its rigidity during process, where employing this metalfor glass to metal sealing, especially'where I am enabled to eliminatethin sections of metal at the juncture of the seal. It will further beobserved that I have provided a form of electrode amenable to quantityproduction methods and which embodies compactness of construction,effecting material economies in the manufacture of this form of device.

It will also be observed that by the construction hereinprovided,rdifiiculties which are involved in sealed-in-glass shellelectrodes, such as sputtering effects, are overcome, and that myconstruction avoids the need for special considto prolong their usefullife.

Having thus described my invention and illustrated its use, what I claimas new and desire to secure by Letters Patent, is-

1. In a luminous discharge device including a glass tubing envelope,drawn adjacent one end section to a substantially uniform diameter, saidend section whereof includes sealed thereto a substantiallycylindrical,A cup-shaped metal electrode of heat resisting chromiumsteel drawn to substantially uniform thickness having a portion thereofadjacent the mouth normally displaced and to which displaced portion theglass is sealed in wiping lap-joint contact, the direction andextensiveness of said displaced portion providing a sealed portionmaking a juncture compensating for a wide tolerance in the glass tubingrby being displaced at an angle in respect of the walls of the electrode,the electrode exposing on the interior surface an effective area forlong life maintenance, the diameter of the glass tubing being of a sizeat least a portion of which is within the minimum displaced portion. ofthe electrode, whereby the electrode and tubing are coaxially aligned bythe said lap joint.

2. In a luminous discharge device including a glass tubing envelope,drawn adjacent one end section to a substantially uniform thicltnese,

end section whereof includes sealed therein a gun stantiallycylindrical, cuochi-ined ele s heat resisting chromium steel it i tiallyto uniform thickness jacent the mouth thereof norme to which flaredportion the wiping lap-joint contact the d :tion and ein tensivenessofsaid flared portici-i providing u sealed portion making a juncturecompensating for a wide tolerance in the glass tubing, the oleo trodeexposing on the interior surface un elfec tive area for long lifemaintenance, the outside diameter of said glass tubing, at its entranceend section being at least greater than the inner diameter of thecylindrical portion oi' said elec-- trode, whereby the electrode andtubing are coI axially aligned.

3. In a luminous discharge device including a glass tubing envelope,drawn adjacent onefend section to a substantially uniform diameter, saidend section whereof includes sealed thereto a substantially cylindrical,cup-shaped metal electrode of heat resisting chromium steel drawnsubstan tially to a uniform thickness, having a portion thereof adjacentthe mouth normally displaced at an angle to form a taper, to theexterior portion of which taper the glass is sealed by a wipinglap-joint, the direction and extensiveness of said taper providingasealed portion making a Juncture compensating for a wide tolerance inthe size of glass tubing, the electrode exposing on the interiorsurface, an effective area for long' life maintenance, the diameter ofthe glass tubing being of a size at least a portion of which is withinthe displaced portion of the electrode.

4. In a luminous discharge device including a glass tubing envelope,drawn adjacent one end` section to a substantially uniform diameter,said end section whereof includes sealed thereto a substantiallycylindrical, cup-shaped metal electrode Bill . shaped metal electrode ofheat resis eration in connection with such devices, in order lap-joint,the direction and extensiveness of said taper providing a sealed portionmaking a iuncture compensating for a wide tolerance in the size of theglass tubing, the electrode exposing onthe interior surface, aneffective area for long life maintenance, the tapered portion includinga lip inwardly of the seal, the diameter of the glass tubing being of asize at least a portion of which is within the displaced portion of theelectrode.

5. In a luminous discharge device including a glass tube envelope ofsubstantially uniform diameter and wall thickness, an end section where-`of includesI sealed thereto by a wiping lap-joint a sumtantiallycylindrical cup-shaped metal electrode of heat resisting steel drawnsubstantially to a uniform thickness, the walls of the electrode beingsubstantially uniform throughout, the

mouth of said electrode being normally ilarcd. the glass being sealed tothe interior surface of said flare portion of said electrode by a wipinglap-joint, the direction and extensivenesc of the :ance

ilared'portion compemating for a Wide t the outside diameter of the saidgli being at least greater than the inner of the cylindrical portion oisaid electi'ci d. In a luminous discharge inc glass tubing envelope, anend section wh cludes sealed thereto a substantially cup-shaped metalelectrode of het drawn substantially to o. uniform t and to the interiorith-ir the glass by a wiping lapmioint, the extenoiveness oi? .salti iluinciting' .it compensating for a' Wide .lera'hce in and a heatconducting coaitially the said electrode.

7. In a luminous dlscl'lurge device in glass envelope, an endsectionwhereo sealed thereto a substantially cylindri .i drawn substantially toa uniform "thic .is .a portion thereof adjacent the mouth being normallydisplaced outwardly, and to which the glass tubing is sealed by a wipinglapjoint, the direction and extensiveness of said outwardly displacedportlon forming a juncture displaced out of the plane of the interiorsurfaces of the electrode, the outside' diameter of said glass tubingbeing at least greater than the minimum internal diameter of theelectrode.

8. In a luminous discharge device, a substan- V tially cylindricalcup-shaped metal electrode of heat resisting chromium steel drawnsubsi/,am

tially to a uniform thickness, the thickness of the said electrode beingnormally outwardly flared of extensiveness and direction to provide acontacting surface for sealing to provide a scalable juncture outsidethe plane of the side walls of said electrode and for forming a wipinglap-joint seal between its surfaces and the glass tubing, and

including a `coaxially disposed heat conducting baille member attachedto the bottom of said electrode at its interior face.

SAMUEL C. MILLER`

